I have a lot of problem trying to sync Ableton Live AND Traktor Pro

Someon Knows how to Sync Traktor Pro 2.6 with Ableton Live 9.1 (MIDI Sync) ??? I already watched ALL the videos tutorial on that matter some time it slightly loose the sync and I can live with that BUT most of the time I receive an error message and Loose completely the sync Iit always result in my audio interface to completely crash (A Pioneer mixer DJM-850 USB audio interface: this is Ableton error message : "The MIDI signal has been lost. (Please check your cable connections and make sure the device sending MIDI Clock is operating correctly. External sync has been turned off » Can ANNY BODY can help me ?

I Have :

MACBOOK PRO OS X 10.9.03 with Intel Core (Quad) i7 2,3 GHZ 16 GB RAM

TRAKTOR PRO 2.6.8 (With KONTROL F1 and 2 KONTROL X1 MKII)

ABLETON LIVE 9.1.2

PIONNER DJM-850 v 1.1.0 (Sample rate in the mixer in ableton and in traktor pro set to 48 KHz sample rate and buffer size set to 1024 samples was 512)